Mechanisms of NaCl-tolerance in acidophilic iron-oxidizing bacteria and archaea: Comparative genomic predictions and insights

Rivera-Araya, Javier; Huynh, Ngoc Dieu; Kaszuba, Marek; Chávez, Renato; Schlömann, Michael; Levicán, Gloria

doi:10.1016/j.hydromet.2020.105334

Cited by 19 publications

(11 citation statements)

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“…We determined that AF46 had higher chloride tolerance at a fixed pH when compared to WT as detected in the preliminary assays. A starting pH of 1.9 was used, which resulted in salt tolerance for iron oxidation in a comparable range to those previously reported in the literature for A. ferrooxidans (16, 31). At 150 mM NaCl, the AF46 completed iron oxidation by 144 hours, but only a small amount of iron oxidation was detected with WT, which stagnated at 120 hours.…”

Section: Resultsmentioning

confidence: 88%

Glutathione synthetase overexpression in Acidithiobacillus ferrooxidans improves halotolerance of iron oxidation

Inaba

West

Banta

2021

Preprint

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Acidithiobacillus ferrooxidans are well-studied iron- and sulfur-oxidizing acidophilic chemolithoautotrophs that are exploited for their ability to participate in the bioleaching of metal sulfides. Here, we overexpressed the endogenous glutamate--cysteine ligase and glutathione synthetase genes in separate strains and found that glutathione synthetase overexpression increased intracellular glutathione levels. We explored the impact of pH on the halotolerance of iron oxidation in wild type and engineered cultures. The increase in glutathione allowed the modified cells to grow under salt concentrations and pH conditions that are fully inhibitory to wild type cells. These results indicate that glutathione overexpression can be used to increase halotolerance in A. ferrooxidans and would likely be a useful strategy on other acidophilic bacteria.

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Section: Resultsmentioning

confidence: 88%

Glutathione synthetase overexpression in Acidithiobacillus ferrooxidans improves halotolerance of iron oxidation

Inaba

West

Banta

2021

Preprint

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“…In E. coli , the genes involved in the Trk system are distributed throughout the genome, however in halophilic organisms trk A and trk H have been found clustered together ( Nakamura et al, 1998 ; Kraegeloh et al, 2005 ). Many acidophile genomes lack trk HG, and only contain the trk A homolog (exception Alicyclobacillus ferrooxidans ) ( Rivera-Araya et al, 2020 ). In Acidihalobacter spp.…”

Section: Resultsmentioning

confidence: 99%

“…Kdp is a high-affinity potassium transport system known to be involved in potassium homeostasis and the osmotic stress response in many bacteria, encompassing halophiles and non-halophiles, and is responsible for the active influx of potassium ions in environments with low potassium concentrations ( Epstein, 2003 ; Strahl and Greie, 2008 ; Kixmüller et al, 2011 ; Price-Whelan et al, 2013 ). The Kdp system is also present in many acidophiles and has been found to be actively transcribed in acidic environments ( Bakker et al, 1987 ; Acuña et al, 2013 ; Cholo et al, 2015 ; Rivera-Araya et al, 2019 , 2020 ; Vergara et al, 2020 ). In E. coli the Kdp system consists of two operons, one encompassing the structural genes kdp FABC, and the other encompassing the regulatory genes kdp DE ( Walderhaug et al, 1992 ).…”

Section: Resultsmentioning

confidence: 99%

Prediction and Inferred Evolution of Acid Tolerance Genes in the Biotechnologically Important Acidihalobacter Genus

et al. 2022

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Acidihalobacter is a genus of acidophilic, gram-negative bacteria known for its ability to oxidize pyrite minerals in the presence of elevated chloride ions, a capability rare in other iron-sulfur oxidizing acidophiles. Previous research involving Acidihalobacter spp. has focused on their applicability in saline biomining operations and their genetic arsenal that allows them to cope with chloride, metal and oxidative stress. However, an understanding of the molecular adaptations that enable Acidihalobacter spp. to thrive under both acid and chloride stress is needed to provide a more comprehensive understanding of how this genus can thrive in such extreme biomining conditions. Currently, four genomes of the Acidihalobacter genus have been sequenced: Acidihalobacter prosperus DSM 5130T, Acidihalobacter yilgarnensis DSM 105917T, Acidihalobacter aeolianus DSM 14174T, and Acidihalobacter ferrooxydans DSM 14175T. Phylogenetic analysis shows that the Acidihalobacter genus roots to the Chromatiales class consisting of mostly halophilic microorganisms. In this study, we aim to advance our knowledge of the genetic repertoire of the Acidihalobacter genus that has enabled it to cope with acidic stress. We provide evidence of gene gain events that are hypothesized to help the Acidihalobacter genus cope with acid stress. Potential acid tolerance mechanisms that were found in the Acidihalobacter genomes include multiple potassium transporters, chloride/proton antiporters, glutamate decarboxylase system, arginine decarboxylase system, urease system, slp genes, squalene synthesis, and hopanoid synthesis. Some of these genes are hypothesized to have entered the Acidihalobacter via vertical decent from an inferred non-acidophilic ancestor, however, horizontal gene transfer (HGT) from other acidophilic lineages is probably responsible for the introduction of many acid resistance genes.

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“…Sediment samples were also used to inoculate in culture media to 1% w/v, and were grown aerobically in shake flasks at 20°C and constant stirring at 180 rpm. The media used were 9K [0.04 g/L K 2 HPO 4 ; 0.01 g/L MgSO 4 *7H 2 O; 0.1 g/L (NH 4 ) 2 SO 4 ; 25.76 g/L FeSO 4 *7H 2 O; pH 1.6] ( Rivera-Araya et al, 2020 ); 9KM1 [0.5 g/L K 2 HPO 4 ; 0.5 g/L MgSO 4 *7H 2 O; 3 g/L (NH 4 ) 2 SO 4 ; 0.1 g/L KCl; 0.01 Ca(NO 3 ) 2 *4H 2 O; 2 g/L MnSO 4 ; 2.1 g/L Al 2 (SO 4 )*18H 2 O; 48 g/L FeSO 4 *7H 2 O; pH 1.6] ( Liu et al, 2007 ); 9KM2 [0.5 g/L K 2 HPO 4 ; 0.5 g/L MgSO 4 * 7H 2 O; 3 g/L (NH 4 ) 2 SO 4 ; 0.1 g/L KCl; 0.01 Ca(NO 3 ) 2 *4H 2 O; 45.22 g/L FeSO 4 *7H 2 O; pH 3.3] ( Dixit et al, 2018 ); and DSMZ 882 [0.132 g/L (NH 4 ) 2 SO 4 ; 0.053 g/L MgCl 2 *6H 2 0; 0.027 g/L KH 2 PO 4 ; 0.147 g/L CaCl 2 *2H 2 O; 18.40 g/L FeSO 4 *7H 2 O; pH 1.8]. The growth of iron-oxidizing cultures was followed by direct counting under an optical microscope with a Neubaüer-Improved chamber (0.02 mm, depth), and by the appearance of a reddish coloration of the medium due to the oxidation of Fe 2+ to Fe 3+ .…”

Section: Methodsmentioning

confidence: 99%

Characterization and genomic analysis of two novel psychrotolerant Acidithiobacillus ferrooxidans strains from polar and subpolar environments

et al. 2022

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The bioleaching process is carried out by aerobic acidophilic iron-oxidizing bacteria that are mainly mesophilic or moderately thermophilic. However, many mining sites are located in areas where the mean temperature is lower than the optimal growth temperature of these microorganisms. In this work, we report the obtaining and characterization of two psychrotolerant bioleaching bacterial strains from low-temperature sites that included an abandoned mine site in Chilean Patagonia (PG05) and an acid rock drainage in Marian Cove, King George Island in Antarctic (MC2.2). The PG05 and MC2.2 strains showed significant iron-oxidation activity and grew optimally at 20°C. Genome sequence analyses showed chromosomes of 2.76 and 2.84 Mbp for PG05 and MC2.2, respectively, and an average nucleotide identity estimation indicated that both strains clustered with the acidophilic iron-oxidizing bacterium Acidithiobacillus ferrooxidans. The Patagonian PG05 strain had a high content of genes coding for tolerance to metals such as lead, zinc, and copper. Concordantly, electron microscopy revealed the intracellular presence of polyphosphate-like granules, likely involved in tolerance to metals and other stress conditions. The Antarctic MC2.2 strain showed a high dosage of genes for mercury resistance and low temperature adaptation. This report of cold-adapted cultures of the At. ferrooxidans species opens novel perspectives to satisfy the current challenges of the metal bioleaching industry.

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Mechanisms of NaCl-tolerance in acidophilic iron-oxidizing bacteria and archaea: Comparative genomic predictions and insights

Cited by 19 publications

References 100 publications

Glutathione synthetase overexpression in Acidithiobacillus ferrooxidans improves halotolerance of iron oxidation

Glutathione synthetase overexpression in Acidithiobacillus ferrooxidans improves halotolerance of iron oxidation

Prediction and Inferred Evolution of Acid Tolerance Genes in the Biotechnologically Important Acidihalobacter Genus

Characterization and genomic analysis of two novel psychrotolerant Acidithiobacillus ferrooxidans strains from polar and subpolar environments

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